A safety arrangement of the above mentioned type is provided, in particular, for a driver-side airbag which is arranged within a steering wheel and is activated in order to protect a driver in the event of an accident or an imminent accident. A steering wheel of this type generally has two horn contacts which are electrically isolated from one another in the installed state and can be electrically contact-connected to one another in the activation state in order to trigger an acoustic horn signal. These horn contacts are fixed in the module support and can be electrically connected to one another by pressing on a pressure plate or switch.
WO2006/076897 A1 discloses a gas generator support for a driver's airbag module to be installed in a steering wheel of a motor vehicle, in which two horn contacts which can be electrically contact-connected to one another are arranged on the generator support. One of the horn contacts is intended to be electrically connected to earth (electrical ground) in the installed state of the generator support, with a fixing region of the generator support for fixing a gas generator being formed and positioned relative to the grounded horn contact such that electrical contact is established between the grounded horn contact and the gas generator when the gas generator is fixed to the fixing region as intended, with the generator support being in the form of an electrical insulator. In this case, the horn contacts are of U-shaped design and one is fixed on a side of the generator support facing a driver and one is fixed on a side of the generator support away from the driver. Deformation of the horn contacts when a pressure is exerted leads to the two horn contacts being electrically connected to one another, with the result that a horn signal is triggered.
The arrangement of the two horn contacts on opposite sides of the generator support, specifically one on the upper side and one on the lower side, is complicated.
The object of the present invention is to provide a safety arrangement and a method with which mounting of the safety arrangement can be simplified and a cost-effective safety arrangement can be provided. According to the invention, this object is achieved by a safety arrangement having the features and methods described and claimed herein. Advantageous refinements and developments of the invention are also described.
The safety arrangement according to this invention includes a module support for an airbag unit and an airbag unit to be installed in a steering wheel in vehicles with at least two horn contacts which are electrically isolated from one another in the installed state and can be electrically connected to one another in the activation state in order to trigger an acoustic horn signal. The arrangement provides for at least one of the horn contacts to comprise a plurality of horn contact sections and for the airbag unit to be electrically conductively connected to the horn contact sections in order to complete the horn contact. Horn contacts are electrically connected to one another by means of switches which are arranged at different locations on the module support; generally, three or four switches are arranged in a uniformly distributed manner, so that the horn contacts can be reliably contact-connected irrespective of where a pressure force is exerted on a pressure plate, for example a front closure of an impact absorber. In order to not provide all the switches with separate cabling, the horn contacts are formed as conductor tracks, so that cabling only has to be provided at a point with the horn contact in each case. If the switches then come into electrical contact both with the first and with the second horn contact, an acoustic horn signal is activated until said horn contacts are electrically isolated. According to the invention, provision is then made for the horn contacts to not connect all points of the switches to one another by means of electrical conductor tracks, but for horn contact sections which are in electrical contact with the airbag unit to be provided on the module support, so that the horn contact sections are completed to form a horn contact which electrically connects all the switch points or switches to one another. Therefore, by virtue of the installation of the airbag unit, an initially open horn contact comprising a plurality of horn contact sections, for example two or three horn contact sections, is closed, so that the two horn contact sections, which are now completed, are electrically connected to one another by activation of a switch, with the result that an acoustic horn signal can be triggered. This reduces costs for the horn contacts and integrates the airbag unit as an electrical conductor element, with the result that functions are integrated.
One development of the invention makes provision for the airbag unit to have a gas generator and an airbag which can be arranged jointly on the module support as part of a steering wheel. In this case, the airbag can be accommodated in a container or a casing, it also being possible for the airbag container or the casing to establish electrical contact with the horn contact sections. As an alternative to this, provision is made for the horn contact sections to be connected to one another by means of the gas generator; a horn contact may optionally be completed by an airbag container, given corresponding electrical isolation between the airbag container and gas generator, while the other horn contact is completed by means of the gas generator. It is also possible for the two horn contacts to comprise a plurality of horn contact sections which are completed by the airbag unit being mounted.
Another development of the invention makes provision for the horn contacts to be arranged on the same side of the module support, that is to say either on the side of the module support facing the driver or on the side of the module support facing away from the driver. In this case, the two horn contacts and the horn contact sections point in the same direction, provided that they are arranged on a flat surface of the module support. The horn contacts can be arranged next to one another on the module support at least in regions, so that substantially parallel conductor tracks are formed on the module support by the horn contacts or horn contact sections.
The airbag unit and the gas generator or the airbag container can be tightly screwed or clipped onto the module support in order to ensure permanent fixing and reliable electrical contact-connection to the horn contact sections.
One development of the invention makes provision for the airbag unit and, in the process, in particular the gas generator to be connected to ground by means of one of the horn contacts in order to prevent electrostatic charging which could lead to unintentional triggering of the gas generator and therefore to unintentional deployment of the airbag.
In order to establish electrical contact between the horn contacts, pressure-operated switches, preferably spring-loaded pressure-operated switches, which can be electrically connected both to one and to the other horn contact, are fixed to the module support. As soon as the two horn contacts are electrically connected to the switch, the horn circuit is closed, so that the horn is activated, with the result that an acoustic horn signal is generated. In this case, the pressure-operated switches are preferably spring-loaded in a manner oriented in the direction of the driver, so that a pressure force has to be exerted in the direction of the steering wheel and the module support in order to electrically connect the horn contacts to one another.
The horn contacts or horn contact sections preferably comprise metal strips or other strips of conductive material, which strips are inserted, preferably integrally formed or injection-moulded, into the module support. Other ways of fixing horn contacts or horn contact sections are possible, for example plugging-in and clamping.
This invention further includes a method for producing a safety arrangement comprising a module support and an airbag unit which is fixed to said module support, in which method two horn contacts are arranged on the module support, makes provision for at least one of the two horn contacts to comprise a plurality of horn contact sections which are fixed to the module support such that they are electrically isolated from one another and are electrically connected to one another by the airbag unit being mounted. By virtue of mounting the airbag unit on the module support, two or more horn contact sections are connected to one another, so that the at least two horn contacts are completed, with the completed horn contacts being electrically isolated from one another in the normal state, that is to say without activation of the horn.
The horn contacts can be clamped or injection-moulded into the module support, with a particularly advantageous variant of the method involving the two contacts initially being of integral design, for example punched out from a sheet-metal blank, and predetermined breaking points being formed between the horn contact sections and the horn contact. Therefore, the two horn contacts or the horn contact and the horn contact sections are initially electrically connected to one another, with this electrical connection being broken at the predetermined breaking points by the predetermined breaking points being broken, with the result that the horn contact sections are electrically isolated from the horn contact. This has the advantage that only one part has to be inserted into an injection-molding die when the horn contacts or horn contact sections are joined to the module support in an injection-moulding process. The electrical bridges along the predetermined breaking points are then removed, so that horn contacts which are electrically isolated from one another or a horn contact and horn contact sections or horn contact sections are formed for two horn contacts which are first closed to form complete horn contacts by the gas generator or an airbag container or the airbag unit being mounted.